diff --git a/CHANGES.rst b/CHANGES.rst
index de057088..35832c60 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -3,12 +3,12 @@
 
 - Remove use of deprecated ``pytest-openfiles`` ``pytest`` plugin. This has been replaced by
   catching ``ResourceWarning`` s. [#90]
-
 - Start using ``pre-commit`` to handle style checks. [#79]
 - Apply the ``isort`` and ``black`` code formatters and reduce the line length
   maximum to 88 characters. [#80]
 - Add spell checking through the ``codespell`` tool. [#81]
 - Drop support for Python 3.8 [#93]
+- Remove ``stdatamodels`` dependency, as it is no longer used. [#91]
 
 0.4.6 (2023-03-27)
 ==================
diff --git a/pyproject.toml b/pyproject.toml
index 45d200f7..3ee4ac07 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -15,7 +15,6 @@ dependencies = [
     'asdf>=2.13',
     'crds>=7.4.1.3',
     'astropy>=5.0.4',
-    'stdatamodels>=0.2.4',
     'importlib_metadata>=4.11.4',
 ]
 dynamic = ['version']
diff --git a/src/stpipe/config_parser.py b/src/stpipe/config_parser.py
index d4301aae..7c69fb3c 100644
--- a/src/stpipe/config_parser.py
+++ b/src/stpipe/config_parser.py
@@ -9,7 +9,6 @@
 
 from asdf import ValidationError as AsdfValidationError
 from asdf import open as asdf_open
-from stdatamodels import s3_utils
 
 from . import utilities
 from .config import StepConfig
@@ -102,13 +101,6 @@ def load_config_file(config_file):
     """
     Read the file `config_file` and return the parsed configuration.
     """
-    if s3_utils.is_s3_uri(config_file):
-        return _load_config_file_s3(config_file)
-    else:
-        return _load_config_file_filesystem(config_file)
-
-
-def _load_config_file_filesystem(config_file):
     if not os.path.isfile(config_file):
         raise ValueError(f"Config file {config_file} not found.")
     try:
@@ -121,22 +113,6 @@ def _load_config_file_filesystem(config_file):
         return ConfigObj(config_file, raise_errors=True)
 
 
-def _load_config_file_s3(config_file):
-    if not s3_utils.object_exists(config_file):
-        raise ValueError(f"Config file {config_file} not found.")
-
-    content = s3_utils.get_object(config_file)
-    try:
-        with asdf_open(content) as asdf_file:
-            return _config_obj_from_asdf(asdf_file)
-    except (AsdfValidationError, ValueError):
-        logger.debug(
-            "Config file did not parse as ASDF. Trying as ConfigObj: %s", config_file
-        )
-        content.seek(0)
-        return ConfigObj(content, raise_errors=True)
-
-
 def _config_obj_from_asdf(asdf_file):
     config = StepConfig.from_asdf(asdf_file)
     return _config_obj_from_step_config(config)
diff --git a/src/stpipe/crds_client.py b/src/stpipe/crds_client.py
index b8ed83ff..24b44ad8 100644
--- a/src/stpipe/crds_client.py
+++ b/src/stpipe/crds_client.py
@@ -12,7 +12,6 @@
 import crds
 from crds.core import config, crds_cache_locking, heavy_client, log
 from crds.core.exceptions import CrdsError
-from stdatamodels import s3_utils
 
 __all__ = [
     "check_reference_open",
@@ -33,7 +32,7 @@ def get_multiple_reference_paths(parameters, reference_file_types, observatory):
     ----------
     parameters : dict
         Parameters used by CRDS to compute best references.  Can
-        be obtained from `~stdatamodels.DataModel.get_crds_parameters`.
+        be obtained from `DataModel.get_crds_parameters`.
 
     reference_file_types : list of str
         List of reference file types.
@@ -81,12 +80,8 @@ def check_reference_open(refpath):
     Ignore reference path values of "N/A" or "" for checking.
     """
     if refpath != "N/A" and refpath.strip() != "":
-        if s3_utils.is_s3_uri(refpath):
-            if not s3_utils.object_exists(refpath):
-                raise RuntimeError("S3 object does not exist: " + refpath)
-        else:
-            with open(refpath, "rb"):
-                pass
+        with open(refpath, "rb"):
+            pass
     return refpath
 
 
diff --git a/src/stpipe/extern/configobj/validate.py b/src/stpipe/extern/configobj/validate.py
index f0d10d62..bfe728ee 100644
--- a/src/stpipe/extern/configobj/validate.py
+++ b/src/stpipe/extern/configobj/validate.py
@@ -163,9 +163,6 @@
 
 import re
 import sys
-from pprint import pprint
-
-from stdatamodels import DataModel
 
 #TODO - #21 - six is part of the repo now, but we didn't switch over to it here
 # this could be replaced if six is used for compatibility, or there are no